Intelligence and law enforcement agencies use various technologies to detect illegal or suspicious activity. The monitoring of electronic activity can assist these efforts. Mobile digital activity of suspicious individuals can sometimes present challenges if, for example, the monitored individual employs techniques to obscure his or her communications or other activity. One of such technique is to carry and interchangeably use two or more mobile devices. If the agencies cannot identify which additional mobile devices are used by the individual, they are unable to effectively monitor the mobile digital activity on those mobile devices.